SE not cranking - Immobiliser?

[mx54nb]

Hi, I've been off the forum for ages, but want to get back into my mx5s again and have a problem.

So my SE has been a garage queen for a few years (comes out say once a month at the most when I can sneak out without the kids), she has developed a nasty habit of not wanting to start...key turns, lights on, fuel pump on, nothing!

I have a battery isolation switch that I can user to "reset" the system and she will start, sometimes immediately, sometimes after many many
attempts.

I initially thought, starter motor is on the way out & had that replaced, but she rewarded me with refusing to start when I picked her up from the mechanics ((who'd just told me the original starter was fine when they bench tested it). I then started to think it was the isolation switch, but figure if that was failing, surely everything would be dead? So, that just leaves me with the immobiliser?? Anyone have any words of wisdom in me tackling this. I don't really enjoy getting stranded when she has really cracked it and having to bump start her.

She has an adaptronic ECU..should this complicate things?

Helen

[greenMachine]

That's a bummer Helen, very frustrating. You say it starts ok when bump started? When it starts, does it run ok?

I don't have much in the way of suggestions, other than to give Mania a ring, they installed a lot of Adaptronics and if it is anything related to the ECU itself, or its installation, they may be able to help. They may also have other suggestions.

If all lights up when the ignition is in the run position, but when you turn the key to activate the starter motor, nothing happens, I'd suspect the ignition switch, or something in the starter circuit - looks like the starter itself is ok having just been replaced. Next time it happens, I'd hold the starter in the 'on' position, and see if I could jiggle the bunch of wires from the ignition switch to see if that made a difference - pretty crude, but that may show something.

Good luck, and keep us posted - hopefully others will chime in with more suggestions.



PS Do you know who did the Adaptronic installation? If it wasn't Mania, that would be the place to start.

[bruce]

Does it maybe need a new battery (after all that time sitting in the garage)? Ya gotta start with the basics and most obvious before moving along.

[ManiacLachy]

I'm not sure how it works with the Adaptronic, but with the Megasquirt standalone ECUs, the immobilizer is bypassed completely. I had to remove the bulb from the cluster to stop it from blinking

However if it start sometimes and not others, and used to be fine, I doubt it's the immobilizer or ECU related. Like Bruce said, the battery would be one thought. Does the car try to start and fail, or just click?

[KevGoat]

As others have mentioned the battery may be first place to start. Check or have checked the battery condition. A bad battery can often still supply "sufficient" power to run certain ancillaries but not enough to run the starter which uses a huge amount by comparison. I'd check all the connections are clean and tight, even a slightly loose orr dirty battery terminal connection can play havoc. Check the earths for the battery and around the engine bay, once again loose connections or dirt and/or corrosion can cause faults. Remove the isolator and see if that makes any difference. My next thought would have been possible problems with the immobiliser/alarm as I had problems with mine and in the end completely removed it and all the associated wires, but Lachy has discounted that as you have an aftermarket ecu.

When left sitting, is the car garaged, carport or in the open? Maybe some corrosion is setting in of a connection or connector somewhere, this can be difficult to locate sometimes.

Oh and yeah, what GM said about the ignition connections under the dash, I had all sorts of similar problems back with my NA with the connector under the steering column. Car had to be transported home about 100kms on one occasion because wouldn't start (everything else worked just like you are saying). Got up next morning and amongst trying other stuff that didn't work, fiddled with the ignition connector under the steering column and it started! Zip ties around the connections and fixing it so it couldn't move at all and it never happened again.

Sent from my SM-G781B using Tapatalk

[greenMachine]

Lachy is right, the immobiliser may still be in position, but it would have been bypassed electronically. The stock ECU needs to see an 'ok' signal from the immobiliser, which interrogates the key's chip (from the ring around the key slot). Aftermarket ECUs can't reproduce the factory ECU<->immobiliser link, and therefore bypass it completely.

Battery/battery terminals/earthing is also a good suggestion. Especially if you can hear 'clicking' when you turn the key but the starter won't operate.

[ManiacLachy]

I'm not 100% sure about the ECU bypass in this case. The old Adaptronics used to run piggyback style, so the immobilizer might still be in play in that scenario.

It's the intermittent nature of the issue that has me discounting the ECU and the immobilizer though.

[mx54nb]

Thanks, yes she runs perfectly fine once going.

Pretty much, start routine is as per normal, let fuel pump prime - and just nothing (apart from the radio powering down for the crank process)
She has been on a trickle charger & the start is lively enough once she kicks over...my Ti is sat right next to her & been abused for even longer...and kicks over 100%.

I'll swap the batteries between them & see what happens...a new battery is my best case scenario

She was set up in Brisbane with Automotive Plus but David has done the tuning on her, I'm due a trip to Mania anyway (well the Ti is as she needs a new roof, and, and, and...my bank a/c is crying already at the thought! Might as well make it a very expensive start to 2023)

[mx54nb]

I'm not 100% sure about the ECU bypass in this case. The old Adaptronics used to run piggyback style, so the immobilizer might still be in play in that scenario.

It's the intermittent nature of the issue that has me discounting the ECU and the immobilizer though.

Yeah, I recalled it was a piggy-back set up...so a little freaked out how upset the set up will get with me having these failed starts

[mx54nb]

Oh and yeah, what GM said about the ignition connections under the dash, I had all sorts of similar problems back with my NA with the connector under the steering column. Car had to be transported home about 100kms on one occasion because wouldn't start (everything else worked just like you are saying). Got up next morning and amongst trying other stuff that didn't work, fiddled with the ignition connector under the steering column and it started! Zip ties around the connections and fixing it so it couldn't move at all and it never happened again.

I shall have a dive under the steeing wheel, I'd mentioned to hubbie that I felt the ignition was "looser" on my SE than on the Ti.

She is garaged but I won't discount corrosion with the wet winters, even my garage had damp issues (had to run a dehumidifier 24-7 to keep it smelling musty). Got me a job for Saturday!!

Thanks Guys, will have a bit of a dig about & see, I certainly wasn't relishing the idea of replacing an immobiliser as that seemed a painful job

Helen

[mx54nb]

Does it maybe need a new battery (after all that time sitting in the garage)? Ya gotta start with the basics and most obvious before moving along.

Thanks, to be honest I'd discounted it as she cranks happily enough once she goes, but I'll swap with my Ti, who does start. Fingers crossed, you're right

[Roadrunner]

I'm not 100% sure about the ECU bypass in this case. The old Adaptronics used to run piggyback style, so the immobilizer might still be in play in that scenario.

It's the intermittent nature of the issue that has me discounting the ECU and the immobilizer though.

Yeah, I recalled it was a piggy-back set up...so a little freaked out how upset the set up will get with me having these failed starts

You have a Select standalone ECU. It won't be the immobiliser, it does function with the Adaptronic, as I have an uncoded key and mine starts but then cuts out 2 seconds later. Yours acts like the wire to the starter is cut - like there's just no signal at all.
I'd also be surprised if it was the battery, since there's times you can flick the kill switch off and on and she'll kick over instantly without hesitation.

As far as I can see the kill switch is just a basic 2 pole unit inline with the battery positive cable, not wired into the starter and ignition system etc, but strange that sometimes flicking it off and on solves the issue, may also just be a coincidence.

I'd be looking into the ignition barrel.
The Miata.net forum has cleaning instructions. https://www.miata.net/garage/CleaningIgnitionSwitch.html

[Roadrunner]

Does anyone know what relays would be in the cranking circuit? Is it possible a relay is getting hung up or is failing, where disconnecting and reconnecting the battery resets it?
Just a thought I had this morning.

[greenMachine]

That might be coincidence. But then, when I had to photograph the ECU terminal block for the installation of my Autronic ECU, the car ran much better after the harness plugs were plugged back in...

I'm firming on the ignition switch/connector, but then I have heard quite a few stories of random problems with Adaptronics so my backup theory is a bad component/connection in the ECU - which might be responsive to a power off/on.

Mania will have seen a lot of these Adaptronics, so one way or another I expect they will quickly get to the bottom of the problem.

[bruce]

Any news regards this problem?